1. Field of the invention
The present invention generally concerns torsional damper devices of the kind comprising at least two coaxial parts mounted to rotate relative to one another within a defined range of relative angular movement and circumferentially acting elastic means disposed between said parts in the circumferential direction resisting such relative angular movement.
2. Description of the prior art
This type of torsional damper is normally incorporated in the design of a clutch disk, particularly for automobile vehicles, in which case one rotating part comprises a friction disk designed to rotate with a first shaft, in practice a driving shaft and the motor output shaft in the case of an automobile vehicle, whereas another of said rotating parts is carried on or itself constitutes a hub designed to rotate with a second shaft, in practice a driven shaft and the gearbox input shaft in the case of an automobile vehicle.
This type of device permits regulated transmission of rotational torque applied to one of its rotating parts where the other is itself subject to a rotational torque. It is thereby able to filter vibrations which may arise at any point in the kinematic system in which it is incorporated, extending from the motor to the driven road wheels in the case of an automobile vehicle.
The present invention is more particularly directed to the case where, in order to delimit relative angular movement between two coaxial parts of a torsional damper device of this kind, there are provided between the latter meshing means, with clearance, cooperating with centering means adapted to urge said coaxial parts in the circumferential direction towards a rest position intermediate the limits of their relative angular movement.
This is the case, for example, in the torsional damper device which is the subject of French Pat. No. 2,242,606 filed Aug. 29 1973 and in the patent of addition thereto No. 2,270,491 filed Apr. 12 1974.
In both cases, the torsional damper device concerned in practice comprises three coaxial parts successively rotatable in pairs and those between which the meshing means with clearance are disposed are those designed to operate at low values of torque.
The centering means provided between these coaxial parts to urge them in the direction towards an intermediate rest position comprise at least one elastic member constituting part of the circumferentially acting elastic means disposed between said coaxial parts, colocated with the meshing means of the latter and adapted, when these coaxial parts are in the rest position, to bear at each of its circumferential ends against a shoulder on each of said coaxial parts.
In the aforementioned French patent No. 2,242,606 and the patent of addition No. 2,270,491 thereto, a helical coil spring is used.
For improved bearing engagement of this spring at its circumferential ends and thus for improved retention in position of the latter there is provided, in the subject French patent and its patent of addition, in association with each of said circumferential ends of this spring a bearing member adapted to be disposed between the latter and the corresponding shoulders of the two coaxial parts concerned.
For appropriate radial retention of a bearing member of this kind and thereby of the elastic centering member, there is further provided, in the patent of addition concerned, on this bearing member and adapted to cooperate with the corresponding shoulders of the coaxial parts concerned, a concave dihedron, said shoulders themselves forming, in the rest position of the assembly, a dihedron which is complementary to that of said bearing member.
In practice, in French Pat. No 2,242,606 and its patent of addition No. 2,270,491, each of the bearing members thus employed is constituted by a plate separate from the elastic centering member with which it is associated.
This arrangement, which has proved and may still prove satisfactory, has the disadvantage of necessitating the use of two distinct parts in addition to the elastic centering member, which increases manufacturing costs and complicates assembly.
A general object of the present invention is an arrangement which, whilst being with advantage able to be employed without modification of other constituent parts of the torsional damper device concerned, permits this disadvantage to be avoided, conferring also other advantages.